<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div class="container">
    <h2 class="page-header">点击切换颜色</h2>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
  </div>
  
  <script>
    //获取div元素对象
    let items = document.getElementsByClassName('item');
  
    //遍历并绑定事件
    for(let i = 0; i < items.length; i++) {
      items[i].onclick = function() {
        //修改当前元素的背景颜色
        this.style.background = 'pink';
      }
    }
  </script>

</body>
</html>